This invention generally relates to determining the fat content of a meat sample, more particularly to determining the fat content by the use of X-ray radiation in such a manner as to automatically calibrate in order to balance X-ray beams as they are attenuated by pairs of simulated meat samples.
In the processing of meat products, there are several occasions when it is important to know exactly the percentage of fat in the meat being processed, and to a lesser extent the percentage of protein and moisture in such meat. Laboratory methods for determining fat percentages have long been known and practiced, which methods typically require a change in the physical or chemical properties of the meat sample, or they otherwise destroy the sample. Additionally, although laboratory analysis techniques typically require from several to 24 hours to complete, they are still practiced because of their accuracy and reliability.
More rapid fat determination is characteristic of devices such as those using X-ray analysis or other techniques. X-ray procedures have the advantage of being both rapid and non-destructive of the meat being analyzed. Known non-destructive means include those shown in U.S. Pat. Nos. 2,992,332, 4,168,431 and 4,171,164. In each of these non-destructive approaches, the operator must manually calibrate the device on a periodic basis in order to maintain the accuracy thereof.
Requiring manual calibration imparts an element of subjectivity that tends to diminish the overall accuracy of these types of devices. Accuracy is an important element that is of substantial economic importance. When fat percentage is measured before meat is ground or otherwise restructured, it is possible to initially prepare products that closely approximate a desired fat content by selection or blending of quantities of meats of differing fat percentages. It is also useful to be able to readily measure the fat content of a product after it has been ground or restructured in order to be able to maintain a certain process control of the product by adjusting the input of fat, protein and moisture into the meat processing system.
In those situations where a meat processing plant attains its meat from a vendor, the price of the meat will vary in proportion to its lean content. Accordingly, it is important to the vendor that the lean content be no higher than the amount specified on the invoice. For the vendor's customers, it is important that they determine that the lean content is no lower than the invoiced amount.
Unless they are carefully calibrated and maintained, X-ray analysis devices are somewhat vulnerable insofar as maintaining their accuracy is concerned due to numerous variables. One important variable is the temperature at the X-ray tube. Generally speaking, the higher the temperature, the greater the number of electrons that are emitted by the tube and directed toward the target in response to a given tube excitation potential. Such temperature changes can be caused by drafts, extensive use, variations in room temperature from time to time throughout the day, and so forth. Such can affect the accuracy of these devices by as much as 2 percent or more, which can be a significant economic difference.
Calibration of these devices also tends to be affected by the number of times that the device is used and the time elapsed since previous calibration. On occasion, when these devices are not properly utilized, decalibration can occur due to movement of the X-ray head with respect to the target. Component parameters can also change, for example, high resistance and high voltage impart significant stresses on the system, the X-ray tube ages, and the feedback resistance from the X-ray tube will change over time of use. When resistance changes as voltage is applied, such changes the kilo electron volts that are operating on the X-ray tube in order to develop the X-rays. Decalibration can also occur on occasion by variations in the power supply input to the unit.
Due to all of these various factors over which the operator has relatively little control, it is necessary to recalibrate these types of devices on a regular basis if accuracy is to be maintained. Calibration of these devices is deceptively simple. A standard that represents a relatively low fat content (for example about 20 percent) is inserted into the sample chamber of the device, and a low-fat calibration potentiometer is adjusted until a digital meter reads the value of the standard, such as 20 percent. Next, the low-fat standard is removed from the sample chamber, and a standard representing a high fat content is inserted thereinto (for example representing a 50 percent fat content), and a high-fat calibrating potentiometer is manually adjusted until the digital meter reads the value of the high-fat standard, such as 50 percent.
Complications arise because the two potentiometer adjustments interact with each other. That is, if the low-fat potentiometer had been set at a value that reads out as 20 percent fat, this value is changed when the other potentiometer is adjusted to give a 50 percent fat reading. Because of this, accurate calibration requires that the process of inserting and removing the pair of standards and adjusting the potentiometers must be repeated several times until no further adjustment is necessary. No further adjustment is necessary when the low-fat standard gives a reading identical to the low-fat standard value (such as 20 percent) and the high-fat standard gives a reading identical to the high-fat standard value (such as 50 percent) without requiring adjustment of either potentiometer so that a subsequent adjustment cannot cause the other potentiometer to move out of adjustment. At this stage, the device is calibrated. As decalibration occurs due to the various factors previously discussed, it is necessary to repeat this procedure. Unfortunately, many operators do not carefully follow this procedure, and their calibration is less than precise.
In many meat processing applications, a variety of meat species are processed from time to time. Typically, in prior art devices, it is necessary to recalibrate the device when changing from species to species, and it would be advantageous to include means that enable the operator to change the species being analyzed by the device without having to recalibrate same. For certain applications, it is desirable to ascertain not only the fat percentage of the meat being analyzed, but also the protein and moisture content thereof.
Accordingly, there is a need for a device that is capable of analyzing the fat content of a meat sample in a non-destructive and rapid manner which substantially eliminates the types of subjective operator involvement and possible operator error that are associated with the prior art devices. Further advantages would be realized, is such a device could be readily varied to account for different species and could also determine the protein and/or moisture content, as well as the fat content.
These various needs and advantages are capable of being attended to by the present invention, which includes automatic calibration to the extent that a pair of calibration standards are inserted into the device and X-ray radiation is transmitted thereto only once for each calibration operation, and the device accounts for the interaction between the individual calibration standards by passing digital outputs generated by the pair of calibration standards through a plurality of data channels. This automatic calibration feature includes the ability to shift, without recalibration, from one meat species to another meat species.
It is accordingly a general object of the present invention to provide improved non-destructive analysis of meat samples.
Another object of this invention is to provide automatic calibration of a device for determining the fat content of meat.
Another object of this invention is to provide an improved meat analysis device that may be particularly compact and portable.
Another object of the present invention is to provide an improved apparatus, method and system for determining the fat percentage of differing meat species without having to recalibrate each time a different species is analyzed.
Another object of the present invention is to provide improved analysis for determining the fat, moisture and protein content of meat, and for adjusting for high, normal or low moisture content of the meat being analyzed.
Another object of this invention is to provide for improved calibration of a meat analysis device that is both automatic and self-inhibiting relative to expected needed recalibration.
Another object of this invention is an improved meat analysis system that includes means for automatically ascertaining the stability of the X-ray signal.